From the utility model documents having publication numbers DE 2004 014 812 U1, DE 20 2004 004 655 U1 and DE 20318 061 U1, circuit arrangements are known by means of which loads can be supplied from one phase of an electrical power supply system. The loads can be loads which vary in operation. The circuit arrangements described in the said utility model documents are provided, in particular, for silicon deposition installations for growing silicon crystals. The loads are here formed by the crystals to be grown. During the operation, the crystals grow and, as a result, change their electrical resistance.
For a particular installation, it is intended to be able to grow distinctly more crystals simultaneously in one reactor. This requires higher powers which is why a three-phase supply with electrical energy is appropriate.
It is a special feature of the reactor that the loads which are formed by the silicon crystals produced are arranged in three concentric circles. Each of these concentric circles comprises a group of silicon crystals, i.e. a group of loads. The number of loads of the load group forming the outer ring is larger than the number of loads of the inner ring.
The voltage curve or current curve traversed during the growing of the silicon crystals should be equal for the loads of a group of loads. Between the groups of loads, however, there can be differences in the current or voltage curves to be maintained. It is appropriate, therefore, to control the current or voltage variation during the growing of the silicon crystals of each load group with a separate control loop.
In contrast, it is also appropriate if an identical number of loads are connected to the three phases of the electrical power supply system. The expert is thus confronted with the requirement of proposing a circuit arrangement which, on the one hand, provides for controlling the three load groups of different size and, on the other hand, ensures a uniform distribution of the loads of the three phases of the power supply system.